This invention relates to an apparatus for the production of moulds composed of identical mould parts produced successively in a pressing chamber from where they are displaced on to a guide pathway on which the mould parts are juxtaposed and advanced in intermittent time with their production.
In an apparatus of this type disclosed in British Specification No. 1,419,592, the guide path is a travelling grate or walking beam conveyor, at least one set of grate bars or beams is both reciprocable in the longitudinal direction of the guide pathway and movable in the vertical direction, whereas the other set of grate bars or beams perferably is prevented from longitudinal movement and is arranged for being raised to the level of the first set of grate bars prior to the initiation of the lowering movement thereof, and for being again lowered after the termination of the raising movement of the first set of grate bars. Such arrangement means that the mould is kept at one and the same level during the stepwise advance thereof, i.e. is not subject to any unwanted movement in the vertical direction and is subject to the necessary step-by-step movement.
In this prior art apparatus the area of the total effective supporting face of each set of grate bars must necessarily be somewhat less than half of the mould bottom area which results in the occurrence of a relatively high specific surface pressure between the mould and the grate bars. In the case of breaks in the normally continuous operation of the apparatus, difficulties may arise due to the fact that after the pouring operation, vapour makes its way towards the outside of the mould, thus also towards its bottom, whereby the compressive strength of the mould sand, on account of its increased moisture content, can be reduced so much that the grate bars form grooves in the mould bottom face. Also, the increased moisture content may make the mould sand so sticky as to cause it to adhere to the grate bars.
Heretofore, these difficulties have been overcome by emptying the guide path in the case of interruptions in the mould part production, i.e. by continuing the advancing of mould subsequent to a casual stop in the production of mould parts.
An object of the invention is to provide an apparatus in which such emptying process becomes unnecessary so that interruptions in the production process will only result in minimum production losses and require no particular attention on part of the operators as far as the function of the guide path is concerned.